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How do you test an antenna?

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gary350

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What equipment is used and how is it done?

I have done a web search it says antennas are ALL tested under the same conditions, same height, same coax, same balun, tested for bandwidth, beanwidth, efficiency, gain, directivity and so forth but it says absolutely what equipment is used and how it is done?????

If I want to test an antenna from across the room how can I do that?????

I am guessing transmit a signal using an RF signal generator and use a scope or spectrum analizer to receive the signal on the antenna being tested?
 
I don't know what you read, but it sounds like crap.

There is only one measure of an antenna. Received power from transmitted power under the given application at the given applications distance and environmental factors.

It's the can you hear me now theory =) If you can, it got through... if not... it didn't...

Anyone that tells you there are absolute standards in relation to RF theory outside of an FCC lab is smoking something...
 
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I guess this question is too hard for everyone.
Not really. Just too generic.
Some of the equipment used for testing antennas:

VSWR meter & RF signal source.
Field strength meter.
Sweep generator/network analyzer.
Megger.

What characteristics are you trying to measure? Gain, radiation pattern, VSWR, bandwidth, etc?
 
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TV antenna.............not a transmitter. Lots of factory antennas out there each one has its own frequency range and bandwidth and beamwidth. Some will not receive high freq very well some don't do well at low freq. I need to find or build an antenna that will recieve all the TV stations in my area. There are 28 available channels but I am only interested in 12 of them. 186 to 692 MHz.
 
That's a pretty wide frequency range, you're not going to find a single antenna that's going to allow you to receive all of those frequencies equally well. What type of antenna are you currently using and what types of antennas have you looked to replace the one you're using now?
 
You are correct. I tried several factory antennas they don't even come close. The antenna I built picks them all up most of the time.

Never mind I figured it out.
 
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Was just wondering what type of antenna you were using, because a highly directional antenna may solve your reception problems, however you'd need an automated mechanical system to turn the antenna towards the stations you wanted to watch.
 
Was just wondering what type of antenna you were using, because a highly directional antenna may solve your reception problems, however you'd need an automated mechanical system to turn the antenna towards the stations you wanted to watch.

I am picking up all the channel I want fine with no rotor. I aimed the antenna at channel 5 that is 322 degrees using a compas it is the hardest channel to receive. I am even receiving channel 7 that is crossville 137 miles away. Lots of movies on 5.3, 7.2, 7.4, 8.1, 8.2, 17, 28.1 and 28.3. Weather channel is 2.2.
 
What type of antenna are you using Gary? I'm curious and you so far haven't given us even a clue.
 
I used the field strength meter on my HDTV to get these readings. The frequency on the left are the 3 channels that I tested it shows a frequency range between 186 to 692 MHz. The antenna screen is 20" wide 36" tall. The elements are 5" from the screen and spaced 9.5" apart vertical and 1.5" apart horizonal. I am using a 300/75 ohm balun and 6 ft of 75 ohm coax to the converter box. The element length and space between the whisker tips were changed to find the maximum signal strength. This test was repeated 3 times. The signals became more stable in the evening after the sun went down. After the first test I saw a noticable pattern the best signal was from element lengths 9" long and 10" long. I also noticed the best signal was whisker spacing of 3" and 4" apart. This test took place upstairs in the house about 18 ft above the ground. The antenna was rotated to pick up maximum signal strength for each element length and each whisker spacing.

Elements length = 8"
Inches between whiskers........2".............3".............4".. ...........5"
692 MHz signal strength........37.............35............38... ..........36
482 MHz signal strength........63.............62............64... ..........65
186 MHz signal strength........42.............40............43... ..........41

Elements length = 9"
Inches between whiskers........2".............3".............4".. ...........5"
692 MHz signal strength........38.............38............43... ..........41
482 MHz signal strength........64.............65............67... ..........67
186 MHz signal strength........49.............51............52... ..........52

Elements length = 10"
Inches between whiskers........2".............3".............4".. ...........5"
692 MHz signal strength........34.............35............39... ..........38
482 MHz signal strength........67.............66............68... ..........65
186 MHz signal strength........56.............55............57... ..........57

Elements length = 11"
Inches between whiskers........2".............3".............4".. ...........5"
692 MHz signal strength........38.............36............36... ..........39
482 MHz signal strength........66.............68............69... ..........64
186 MHz signal strength........44.............53............53... ..........52

A final test was done using only elements 9" and 10" long spaced 3" and 4" apart.

Elements length = 9"
Inches between whiskers........3".............4"
692 MHz signal strength........35............34
482 MHz signal strength........62............61
186 MHz signal strength........51............50

Elements length = 10"
Inches between whiskers........3".............4"
692 MHz signal strength........34............34
482 MHz signal strength........68............64
186 MHz signal strength........49............50

Next I did one more test I made the screen larger from 20"x36" to 36"x36". The signal became much more stable. Fluxuation in signal changed for example, 67 to 69 are now holding steady at 71. There was almost no noticable increase in signal strength at 692 MHz.

Elements length = 9"
Inches between whiskers........3".............4"
692 MHz signal strength........32............33
482 MHz signal strength........65............66
186 MHz signal strength........69............69

Elements length = 10"
Inches between whiskers........3".............4"
692 MHz signal strength........39............34
482 MHz signal strength........69............69
186 MHz signal strength........71............72

Next I experemented with the element diameter #14 wire, #10 wire and #8 wire. No signal difference was noticed.

The purpose of this test was to learn why I am having so much trouble receiving channel 5 = 692 MHz and what can be done to solve the problem. A larger screen and changing the space between the whisker tips has improved the signal on channel 5. When I checked it the other day signal went up from 35 to 44. Much stronger signal with no drop outs.

Now I also receive channel 7 most of the time which is 137 miles away. I have no idea how this is happening but it is. Channel 7 is on the back side of the antenna. The antenna is aimed at 322 degrees and channel 7 is at 90 degrees. It has to be a reflected signal.
 
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That kind of grid array will give you a highly directional pattern, about 12db of directional gain.
I think you'd be surprised at what you could pick up at distance with a rotatable array.
 
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